Cascade amplifier



March 14, 1933. A. HUND 1,901,558

CASCADE AMPLIFIER Filed July 22, 1930 INVENTOR August Hund TTORNEY Patented Mar. 14, 1933 i UNITED-1 STATES,

nucus 'r HUND, or WE-ST ORANGE, NEW JERSEY, 'As's'IeNon 'ro WIRED nanio, rim, or

NEW YORK, n.1, A conroanr'ron or DEL RE.

some A'urmrma V Ipfllication filed my 22,1930. Serial No. 469,8 1

My invention pertains in general to' cascade amplifiers and-specifically-relates to a cascade amplifier which employs a photoelectric cell. v v

5 In my cO- ending application; serial numi ber 460,590, filed June 12, 1930, patented June 14, 1932, No. 1,863,052, I have disclosed a photoelectric cell producing a substantially elongated electronic stream under control of any external electrostatic-grid.

One of the objects of my present inven-; tion consists in providing a cascade amplifier employing a'plurality of photoelectric cells having external electrostatic grids.

resistance coupled multi-stage amplifier sys term in which external grids form the controlling electrodes of a plurality of photoelectric cells producing substantially elongated electronic streams. Another object consists in producing 'a .multi-stage photoelectric cell amplifier system in which the characteristic ofeach stage. of amplification can be altered by adjusting the relative position of the grid and cathode of the photoelectric cell. 1 v

I accomplish the above desirable objects in a novel cascade amplifier system employ-. ing a photoelectric cell of the type disclosed in my co-pending application before referred to. 1 I In the drawing I have diagrammatically illustrated one embodiment of the cascade" amplifier system of my invention.

Referring to the drawing, an inductance 1 and. capacitance 2.comp rise an input circuit for my amplifier system, This inputcircuit can be tuned ..to resonance with an alternating input current. of definite frequency induced in the inductance 1. It will,

of course, be understood that this input 'circuit is merely indicative of an input source commonly used with multi-stage amplifier systems. Any other suitable source of input current could be-equally well employed with my amplifier system.

The input circuit is connected, as shown,

to the grid 3 and the cathode 4 of the photoelectric cell 5. The grid 3 is an annular electrode exteriorly positioned on the tubu- A further object comprises'produc ing a.

' cells of my invention, and when irradiations ar containing'envelope' of the photoelectric cell. 5 in a manner adapted to produce an anotherphotoelectric cell-8. The anode 9 of the photoelectric cell 8 is directly connected to the grid electrode 10 of another photoelectric cell 11. The cathodes l2 and 13 ofthe photoelectriccells 8 and 11 are connected in parallel with the cathode 4..

The battery 14, or other suitable source: of current, is connected on its negative-side to the cathodes 4, 12, and 13. 'The positive side of the-battery 14 is connected in parallel to the resistances 15 and 16-, and an indicating device 17 The resistances 15 and 16 are connected tothe anodes 6 and 9 respectively,

while the indicating device .17 is connected to the anode 18 of the photoelectric cell 11. The resistances 15 and 16 are of a value adapted to provide a suitable potential drop across the anodes and cathodes of the photoelectric cells 5 and 8 respectively. The indicating device 17 can be a telephone, a meter, or any instrument for indicating current flow, I or may be a work circuit. A fixed capacitan'ce 19 is connected in parallel with the battery 14 to form a by-pass condenser.

Such an-arrangement inwhich a plate of one electron discharge device is connected to thegrid of a succeeding electron discharge device comprises what is commonly known as acascade or tandem connection. 7 Cascade or tandem connections for thermionic 'electron discharge devices used as amplifiers are well known in the art.

When the proper voltages are applied tothe interior electrodes of the photoelectric are directed upon the cathodes thereof, a substantially elongated electronic stream,

' will be produced from cathode to anode in each' cell. The annular exterior electrodes 0 serve to control the electronic stream in each cell. It is an es ecial. feature of the photoelectric cell disc osed in my copending ap plication before referred to that the, exterior grid electrode can be moved with reference to the interior cathode, thereby altering the characteristic of the photoelectric cell. I A variable current applied at the input circuit 12 will set up an electrostatic field at the grid electrode 3 and which acts on the electronic stream produced from the cathode. 4 to the anode 6 of the photoelectric cell 5. The electronic stream is therefore influenced in accordance with this electrostatic field.' The variations of these electrostatic charges I are consequently amplified in the plate cur rent of the photoelectric cell This plate current is directly applied'to the grid 'electrode 7 of the next photoelectric cell 8. The grid electrode 7 influences the electronic stream from cathode -12 to anode 9to-furthcir amplify the variations of theoriginal input current. The outputof the photoelectric cell 8 is then applied to the control grid 10 of the next photoelectric cell '11, The va- I riations are further amplified. in the same manner. The output of the final photoelectric cell 11 is then delivered to the indicating device 17. It will of coursebe understood that any number of photoelectric cells could be equally well arranged in asimilar manner to reduce cascadeamplification. 1

t will be noted that the'couplings betweenthe photoelectric cells are essentially of the trolling electrodes, in e ect, form the'capa'ci tance components of theresistance-capacitan'ce couplings. This" arrangement avoids the introduction of extraneous:capacitancesi 40 in the amplifier circuit which areoftenas couplings to control grids in usual thermionic amplifier systems. 1

It will now be obvious that I have prothat many advantages will be derived from the use ofsuch a system. A particular advantage resides in the feature of adjustment of the grid with reference to the cathode whereby the characteristic of the photoelectric cell can be changed.

Although I have shown a preferred embodiment of my amplifier, it is to be understood that many changes will readily occur to those skilled in the art, but which will not depart from the intendedscope of my invention. I do not therefore desire to limit myself to the foregoing except insofar as may be pointed out in the appended claims. What I claim as new and original and desire to secure by Letters Patent of the- United States is:

1. An amplifier system comprising, an input circuit, a plurality of photoelectric cell's, each of which includes an interior anode, an

. resistance-capacitance t pe, but that the con--,

vided a novel form of cascade amplifier and ,ota

interior cathode, and an'exterior grid; and, an output circuit, said photoelectric cells being directly connected in tandem from plate to grid. v

2. An amplifier system comprising, an input circuit, a plurality of electron discharge tubes each of which is adapted to produce photoelectric emission and which arecon v nected in series by resistance-capacitance couplings, the capacitance component of said couplings being adapted to set up an electro; static field which directly controls said photoelectric emission, and an output circuit for said discharge-tubes; y

j 3. An .amplifiersystem comprising, a plurality ofv electron discharge tubes each having a photosensitive cathode, and' an anode adapted to produce a substantially elongated electronic stream, an external control elec trode fo'r each of said electron discharge tubes, an inputlcircuit included between the control electrode and cathode of one of said electron.dischargetubes, an output circuit included between the anode and cathode of another of said electron discharge tubes, and cascade connections between said electron discharge tubes in which the anode of one tube is directly connected to the control electrode'of the succeeding tube, all of said control electrodes being movable wherebysaid 95 control electrodes can; be individually ad-= justed' for. best conditions of amplification for. said tubes. v AUGUST 7 sociated with the connections from such" 

